This invention relates in general to heating apparatus and deals more particularly with improved electromagnetic induction apparatus for heating liquid. The general aim of the present invention is to provide an improved electrically operated liquid heating apparatus which may be safely operated in any environment and which includes a heating unit which contains one or more electromagnetic induction heaters releasably supported and arranged for convenient access to facilitate servicing or replacement. The apparatus of the present invention may, for example, be arranged in a closed loop to continuously circulate a quantity of liquid heated to a predetermined temperature as, for example, in a heating system for a building or in a lubrication system. The present apparatus is also particularly well suited to receive liquid such as fuel oil from a supply source or storage tank and to supply it at a higher temperature to a remote location where it may be efficiently utilized to fire a boiler or the like.